Dataset Information

Molecular phylogenetic study of the tribe Tropidieae (Orchidaceae, Epidendroideae) with taxonomic and evolutionary implications.

ABSTRACT: The orchid tribe Tropidieae comprises three genera, Tropidia, Corymborkis and Kalimantanorchis. There are three fully mycoheterotrophic species within Tropidieae: Tropidia saprophytica, T. connata and Kalimantanorchis nagamasui. A previous phylogenetic study of K. nagamasui, based only on plastid matK data, placed K. nagamasui outside the clade of Tropidia and Corymborkis without support. In this study, we performed phylogenetic analyses using a nuclear ribosomal DNA spacer (ITS1-5.8S-ITS2), a low-copy nuclear coding gene (Xdh) and a mitochondrial intron (nad1b-c intron) to study the phylogenetic relationships within Tropidieae. We included six photosynthetic and all three fully mycoheterotrophic Tropidieae species. The resulting phylogenetic trees placed these fully mycoheterotrophic species inside the Tropidia clade with high support. In our trees, these three species do not form a monophyletic group together, because the photosynthetic T. graminea is nested amongst them. Our results also suggest that the loss of photosynthetic ability occurred at least twice in Tropidia.

SUBMITTER: Sabino Kikuchi IAB

PROVIDER: S-EPMC7044249 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Molecular phylogenetic study of the tribe Tropidieae (Orchidaceae, Epidendroideae) with taxonomic and evolutionary implications.

Sabino Kikuchi Izai A B IAB Keßler Paul J A PJA Schuiteman André A Murata Jin J Ohi-Toma Tetsuo T Yukawa Tomohisa T Tsukaya Hirokazu H

PhytoKeys 20200219

The orchid tribe Tropidieae comprises three genera, Tropidia, Corymborkis and Kalimantanorchis. There are three fully mycoheterotrophic species within Tropidieae: Tropidia saprophytica, T. connata and Kalimantanorchis nagamasui. A previous phylogenetic study of K. nagamasui, based only on plastid matK data, placed K. nagamasui outside the clade of Tropidia and Corymborkis without support. In this study, we performed phy ...[more]

PMID: 32132858

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Project description:Miconieae is the largest tribe in the Melastomataceae with over 1,850 species. The members of Miconieae display a wide range of morphological diversity, and seed morphology is no exception. Previous studies have found that seed morphological diversity is not congruent with traditional classifications, and suggest that it may reflect evolutionary relationships within Miconieae. Here we characterize seed morphology of 364 species of Miconieae. The morphological data set and a DNA sequence data matrix were analyzed under a parsimony and Bayesian framework. Seed characters were used to test taxonomic and clade hypotheses, to estimate morphological ancestral character states, and to assess phylogenetic signal. The phylogenetic analyses of morphological data retrieved a poorly-resolved, low-supported phylogeny; in contrast, a relatively strongly supported phylogeny was estimated using the molecular data. Hypothesis testing procedures could only reject the monophyly of Clidemia, Leandra, and Miconia. The results indicated that the seed morphological characters were homoplasious, but contained phylogenetic signal. The morphological seed types that were described in previous studies did not support any of the clades retrieved by the molecular phylogeny. In contrast with previous investigations, our study shows that although seed morphology is very variable, it does not provide information for supporting some genera or clades within Miconieae. However, it is suggested that seed characters in combination with other vegetative and reproductive traits may aid in the characterization of smaller clades. The presence of phylogenetic signal retrieved by homoplasious characters may indicate that diversification of seed characters could have an adaptive component. Further studies that increase taxon sampling, refine seed trait characterization, and evaluate the alleged relationships between environmental variables and seed diversification will contribute to a better understanding of seed morphology and evolution in this species-rich tribe.

Project description:Background and aimsThe largest subfamily of orchids, Epidendroideae, represents one of the most significant diversifications among flowering plants in terms of pollination strategy, vegetative adaptation and number of species. Although many groups in the subfamily have been resolved, significant relationships in the tree remain unclear, limiting conclusions about diversification and creating uncertainty in the classification. This study brings together DNA sequences from nuclear, plastid and mitochrondrial genomes in order to clarify relationships, to test associations of key characters with diversification and to improve the classification.MethodsSequences from seven loci were concatenated in a supermatrix analysis for 312 genera representing most of epidendroid diversity. Maximum-likelihood and parsimony analyses were performed on this matrix and on subsets of the data to generate trees and to investigate the effect of missing values. Statistical character-associated diversification analyses were performed.Key resultsLikelihood and parsimony analyses yielded highly resolved trees that are in strong agreement and show significant support for many key clades. Many previously proposed relationships among tribes and subtribes are supported, and some new relationships are revealed. Analyses of subsets of the data suggest that the relatively high number of missing data for the full analysis is not problematic. Diversification analyses show that epiphytism is most strongly associated with diversification among epidendroids, followed by expansion into the New World and anther characters that are involved with pollinator specificity, namely early anther inflexion, cellular pollinium stalks and the superposed pollinium arrangement.ConclusionsAll tested characters show significant association with speciation in Epidendroideae, suggesting that no single character accounts for the success of this group. Rather, it appears that a succession of key features appeared that have contributed to diversification, sometimes in parallel.

Dataset Information

Molecular phylogenetic study of the tribe Tropidieae (Orchidaceae, Epidendroideae) with taxonomic and evolutionary implications.

Publications

Molecular phylogenetic study of the tribe Tropidieae (Orchidaceae, Epidendroideae) with taxonomic and evolutionary implications.

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